Surgical instrument with a dissecting tip

ABSTRACT

A surgical instrument useful in harvesting blood vessels such as veins and arteries. The instrument has a pair of jaws and a central cutting element displaceable distally and proximally to dissect tissue contained between the jaws. The distal ends of the jaws form a dissecting tip.

FIELD OF THE INVENTION

The present invention relates, in general, to bipolar electrosurgicalinstruments and, more particularly, to bipolar electrosurgicalinstruments incorporating offset electrodes.

BACKGROUND OF THE INVENTION

Surgeons and surgical assistants have been using medical devicesincorporating radio frequency (RF) electricity for many years tocauterize and coagulate bodily tissues during surgical procedures. Twotypes of RF surgical devices are conventionally utilized: mono-polar andbipolar. Both incorporate a pair of conductors for transmission ofalternating RF electricity. In a mono-polar electrosurgical instrument,a first conducting electrode having a first polarity is typically placedon the patient's skin and communicates through the body, i.e. forms aconductive path, with a second conducting electrode having the oppositepolarity located on the surgical instrument. A bipolar electrosurgicalinstrument, however, typically incorporates both first and secondelectrodes of opposite polarity in the same surgical instrument,substantially restricting the flow path of electric current to tissuethat is contained between the electrodes. As mentioned previously, bothmono-polar and bipolar electrosurgical instruments apply RF energythrough tissue. The energy is dissipated within the tissue in the formof heat due to the natural impedance of tissue. As the temperature ofthe tissue rises, the electrical resistivity of the tissue increases.When RF energy is applied to tissue, and as the temperature reachesabout 67-70 degrees Celsius, the tissue begins to coagulate. Asincreasing amounts of energy dissipate in the tissue, the collagenforming the tissue matrix breaks down and appears to “melt”. Mechanicalcompression of the coagulating tissue layers fuses and seals anycontained blood vessels, so that the tissue may be cut without bleeding.When the tissue temperature reaches 100 degrees C., most fluids(including water) vaporize into the surrounding tissues and air.

The energy dissipation rate in tissue depends on numerous factors,including the inherent electrical resistivity of the tissue and theelectrical current density. Electrical current density in varioustissues is an important consideration in the design of the electrodes ina bipolar electrosurgical instrument, including the number, size, shape,and placement of the electrodes.

Many surgeons prefer to use bipolar electrosurgical instruments forhemostatically (without bleeding) sealing tissue prior to transection.Bipolar electrosurgical devices are known for grasping, coagulating, andcutting tissue.

Typically the instruments have grasping elements, and one of thegrasping elements is an electrically opposite pole of the other graspingelement. For this type of conventional, bipolar electricalconfiguration, electrical current can be simplistically thought of as“flowing” from one grasping element (a positive pole), through thegrasped tissue, and to the other grasping element (a negative pole).When tissue held between the grasping elements is coagulated, it isknown that the electrical resistivity of that portion or zone of tissueincreases dramatically. This causes the electrical current to seek a newpath of lesser electrical resistivity around the zone, resulting in aspread to tissue adjacent to the outside of the grasping elements.Accordingly, it is believed that the zone of coagulated tissue continuesto increase laterally from the grasping elements. The final width of thecoagulation zone depends on several factors, including the power settingof the electrosurgical generator, and on the length of time the operatorapplied electrical energy to the tissue, etc. It is typical for anoperator to apply electrical energy (usually by stepping on a footactuator) for several seconds more than is actually needed to ensurethat the grasped tissue is completely coagulated prior to cutting toprevent bleeding. If the amount of tissue grasped is very small,coagulation of the grasped tissue may occur so quickly that the operatorcannot stop the application of electrical energy quickly enough toprevent excessive lateral spreading of the coagulation zone. Inaddition, the operator may not always be able to visualize the spreadingof the coagulation zone because of obstructing tissue structures,especially during an endoscopic procedure; or, because the coagulationof the tissue occurs on the inside of the tissue or blood vessel.

Excessive lateral spread of the coagulation zone may be harmful topatients undergoing surgical procedures in which an organ or vessel isharvested for use in the same or a different patient. For example, in acoronary artery bypass graft (CABG) procedure, a surgeon or surgicalassistant may remove a saphenous vein from one of the patient's legs touse as one or more bypass grafts on that patient's heart. In recentyears, new surgical dissecting/retracting tools have been introduced toenable the surgical operator to harvest the saphenous veinendoscopically. Examples of endoscopic vessel harvesting devices andmethods are contained in the following U.S. Patents, which areincorporated by reference: U.S. Pat. No. 5,667,480; 5,722,934;5,928,135; and 5,928,138. In such surgical procedures the operator“tunnels” with the surgical dissecting/retracting tool alongside thevein under the skin, working through a small incision made into theinside of the patient's leg or knee. The benefits of this procedure tothe patient are numerous because endoscopic vein harvesting (EVH)results in greatly reduced recovery time and pain for the patient ascompared to the earlier open procedure of creating an incision along theleg equal to the length of the vein harvested. In addition scarring islimited, and the incidence of serious infections reduced.

In conventional EVH procedures, the surgical operator uses the surgicaldissecting/retracting tool to create a small working space at the distalend of the tool and adjacent to the vein being harvested. As theoperator maneuvers the tool along the vein to separate the vein fromadjacent tissues, the operator typically encounters numerous smallercollateral vascular side branches of the main vein (usually about 15).To harvest the main vein with minimal bleeding of surrounding tissues,the operator may apply at least two conventional surgical clips to eachside branch encountered, using a conventional mechanical endoscopicsurgical clip applier. Then the clip applier is removed, an endoscopicscissors is inserted to cut the side branch between the applied clips.Each instrument insertion and removal is not only time-consuming, butcare must be taken not to cause trauma to the vein being harvested andto surrounding tissues in the leg. The operator may also use bipolarelectrosurgical scissors in place of mechanical clip appliers, which arewell known in the art for use in this type of surgical procedure.However, bipolar scissors may induce undesirable lateral spreading ofthe coagulation zone if not used correctly, and the experience of theoperator is crucial in preventing injury to a harvested vein to be usedin the CABG procedure. When using bipolar scissors or any of the otherconventional electrosurgical instruments during an EVH procedure, theoperator is required to treat each side branch at a location as fardistant laterally from the main vein as practical, and the operator mustapply RF energy for a minimal time to seal the side branch for cutting.

Various embodiments of a relatively new kind of bipolar, electrosurgicaldevice are disclosed in the following patents hereinafter referred tocollectively as the “offset electrode device”, and are incorporated byreference herein: U.S. Pat. No. 5,403,312; U.S. Pat. No. 5,709,680; andU.S. Pat. No. 5,833,690. In the offset electrode device, the bipolarelectrodes have an “offset” configuration and coagulation of tissue issubstantially confined to only the tissue held between a pair ofinterfacing surfaces. The offset electrode devices also provide for hightissue compression to coagulate tissue uniformly and to force fluid outof the coagulation zone. Such fluid would vaporize during coagulationand shoot laterally from the interfacing surfaces, possibly causingthermal injury to adjoining tissue. The offset electrode devicesdisclosed, however, in the referenced patents are not specificallyadapted for use in endoscopic vein harvest procedures or in other typesof minimally invasive surgical procedures requiring 5mm diameterendoscopic ports. There is a need in this art for a bipolarelectrosurgical instrument that may be used through a five millimetertrocar port, and that has minimally sized jaws for improved access andvisualization of tissue structures in the surgical site.

Another concern of the surgical operator when using any electrosurgicalinstrument is the tendency of coagulated tissue to stick to the jaws ofthe instrument during operation of the instrument. The operator musttake additional time to manipulate the instrument to release tissueadhering to the end effectors, possibly injuring surrounding tissue,especially when operating in limited working spaces during endoscopicprocedures. Adhering tissue also reduces the electrical conductivity ofthe bipolar electrodes and it is often necessary for the operator tomanually clean the electrodes in order to continue using the instrument.This is especially prevalent for forceps-type grasping instrumentsincorporating the conventional bipolar electrode (non-offset)configuration.

Many conventional surgical instruments incorporate cutting blades fortransecting tissue held within the jaws. A potential difficulty withcutting blades of such instruments is “tissue-tagging” when the bladedoes not completely cut through all the tissue held in the jaws. Thismay occur, for example, if the cutting edge of the blade is dull ornicked. Another reason tissue-tagging may occur, or even some bleedingafter the tissue is coagulated and cut, is that the tissue is not heldfirmly enough within the jaws of the instrument as the cutting blade ispassed through the tissue held. When tissue is initially clamped withinthe jaws of the instrument, the clamping force may be very high due tothe elasticity of the fluid-containing tissue. But after the tissue hasbeen compressed for a period of time, and then is coagulated, most ofthe fluid has been driven out of the tissue, with the result that theelasticity of the tissue is greatly reduced. The clamping force on thetissue is also decreased so that the tissue may shift within the jaws asa cutting blade is passed through it. This presents the possibility thatnot all the tissue will be cut, or the cutting blade will pass through aportion of tissue that is not fully coagulated.

During some surgical procedures, including the EVH procedure, thesurgical operator must cut and dissect a first tissue structure awayfrom a second tissue structure prior to performing a transection orother surgical procedure on the second tissue structure. A conventionaltechnique for this type of surgical cutting and dissecting used a pairof conventional, mechanical scissors held in an open configuration, thusforming a vee-shape with the scissors blades. The scissors blades arethen advanced between the first and second tissue structures to cut andseparate them. At this point, the surgical operator may remove thescissors and continue the surgical procedure with another surgicalinstrument such as a clip applier for ligation of the second tissuestructure. During an EVH procedure, the exchange of endoscopicmechanical scissors and the clip applier in and out of the working spacemay occur many times, increasing the time to perform the procedure, andpossibly injuring the vein or surrounding tissue. An alternative tousing a mechanical scissors together with a clip applier is to use abipolar electrosurgical scissors as described previously. Usingconventional bipolar coagulation and cutting devices may result inexcessive lateral spreading of the thermally affected zone of tissue,especially if the operator is inexperienced or otherwise not careful.

Another shortcoming when using currently available electrosurgicalcutting instruments with cutting blades is that the cutting blade may beexposed accidentally to adjacent tissue when the operator does notintend to cut the tissue.

Accordingly, what is needed in this art is a bipolar electrosurgicalinstrument incorporating offset electrodes and compression zones, asdescribed for the offset electrode device, yet improved to be lesssurgically invasive and to provide better access and visualization atthe surgical site. There is also a need for a bipolar electrosurgicalinstrument that easily releases tissue from the jaws after each cycle ofuse, and automatically wipes electrode surfaces clean for each cycle ofuse. Additionally, there is a need for an instrument having more thanone cutting blade that cuts through the tissue held within the jaws toimprove the probability of completely transecting the tissue held, butwithout increasing the size or cost of the instrument. There is also aneed for an instrument that provides for additional clamping force to beapplied to tissue held in the jaws immediately prior to passing acutting blade through the tissue. There is yet a further need for aninstrument that safely coagulates tissue without excessive lateralthermal spread, and which reduces the need for using mechanical scissorsand clip appliers during a surgical procedure. Replacing a scissors anda clip applier with a single bipolar electrosurgical cutting instrument,for example, and reducing surgery time by reducing the number ofinstrument exchanges during the surgical procedure, allows a significantcost savings to the hospital, and is beneficial to the patient. There isalso a need for an electrosurgical instrument with a cutting blade thathas an operational sequencing element that allows the movement of thecutting blade through a tissue grasping region only when the jaws arefully closed, thus reducing the possibility of accidentally injuring thepatient.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a bipolarelectrosurgical instrument incorporating offset electrodes andcompression zones, that is less surgically invasive and that providesbetter access and visualization at the surgical site.

It is another object of the present invention to provide a bipolarelectrosurgical instrument that easily releases tissue from the jawsafter each cycle of use, and automatically wipes electrode surfacesclean for each cycle of use.

It is yet another object of the present invention to provide aninstrument having more than one cutting blade that cuts through thetissue held within the jaws to improve the probability of completelytransecting the tissue held, but without increasing the size or cost ofthe instrument.

It is still yet another object of the present invention to provide aninstrument that provides for additional clamping force to be applied totissue held in the jaws immediately prior to passing a cutting bladethrough the tissue.

Yet another object of the present invention is to provide an instrumentthat safely coagulates tissue without excessive lateral thermal spread,and which reduces the need for using mechanical scissors and clipappliers during a surgical procedure.

Still another object of the present invention is to provide anelectrosurgical instrument with a cutting blade that has an operationalsequencing element that allows the movement of the cutting blade througha tissue grasping region only when the jaws are fully closed, thusreducing the possibility of accidentally injuring the patient.

Accordingly, a tissue dissecting surgical instrument is disclosed. Theinstrument has a handle having a distal end, a proximal end, a top, anda bottom. There is a shaft having a proximal end, a distal end, and alongitudinal axis. The proximal end of the shaft is mounted to theproximal end of the handle. A first jaw and an opposed second jaw aremounted to the distal end of the shaft. The first and second jawsmovable are relative to each other from an open position for positioningtissue. Each jaw has a proximal end and a distal end. The first jaw hasa first channel and the second jaw has a second channel, wherein thefirst and second channels form a cutting tunnel when the first andsecond jaws are in the closed position. An elongated member is slidablymounted to the shaft. The elongated member has a proximal end and adistal end. A cutting element is movable within the cutting tunnel tocut tissue positioned between the first and second jaws in the tissuegrasping region, and the cutting element is mounted to the distal end ofthe elongated member. The cutting element has a first blade and a secondblade. The cutting element is movable in the cutting tunnel from acentral position to both a proximal position proximal to the tissuegrasping region and a distal position distal to the tissue graspingregion. The first blade cuts tissue positioned between the first andsecond jaws in the cutting region when the cutting element moves fromthe central position to the proximal position, and the second blade cutstissue positioned between the first and second jaws in the cuttingregion when the cutting element moves from the proximal position to thecentral position. An actuating member is mounted to the handle such thatthe proximal end of the elongated member is mounted to the actuatingmember. A dissecting tip is formed by the distal ends of the first andsecond jaws. The dissecting tip has a distal end used for tissuedissection, and which covers the cutting element when the cuttingelement is in the central position so that adjacent tissue is shieldedfrom the first and second cutting blades. The cutting tunnel extendsthrough the distal end of the dissecting tip and is in communicationwith an opening in the distal end of the dissecting tip, such that whenthe cutting element is moved from the central position to the distalposition, at least a section of the second cutting blade extends out ofthe cutting tunnel and out through the opening in the dissecting tip andso that the second cutting blade may engage tissue adjacent to thedissecting tip.

Yet another aspect of the present invention is a method of surgicallydissecting tissue using the above-described surgical instrument.

The foregoing and other features and advantages of the present inventionwill become more apparent from the following description andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an electrosurgical clamping, coagulating,and cutting instrument of the present invention shown connected to aschematic of an electrosurgical energy generator.

FIG. 2 is an isometric view of the distal section of a tube assembly ofthe instrument of FIG. 1, shown with an upper jaw in an open position.

FIG. 3 is an isometric view of the distal section of the tube assemblyof the instrument of FIG. 1, shown with the upper jaw in a closedposition.

FIG. 4 is an exploded, isometric view of the distal section of the tubeassembly of the instrument of FIG. 1.

FIG. 5 is a cross-sectional view of the distal portion of the tubeassembly taken through View-Line 5—5 of FIG. 3.

FIG. 6 is an exploded, isometric view of a handle assembly of theinstrument of the present invention.

FIG. 7 is a side view of the interior of the handle assembly of theinstrument of the present invention with the left handle shell removed,illustrating the actuators in positions to maintain the upper jaw in anopen position and the cutting element in a central position.

FIG. 8 is a top view of the handle assembly of FIG. 7, with the left andright handle shell assembled.

FIG. 9 is a longitudinal, sectional view of the distal section of thetube assembly of FIG. 7.

FIG. 10 is a side view of the handle assembly of the instrument of thepresent invention with the left handle shell removed, illustrating theactuator positioned such that the upper jaw is in a closed position andthe cutting element is in a central position.

FIG. 11 is a top view of the handle assembly of FIG. 10 with the lefthandle shell assembled with the right handle shell.

FIG. 12 is a longitudinal, sectional view of the distal section of thetube assembly of the instrument of FIG. 10.

FIG. 13 is a side view of the handle assembly of an instrument of thepresent invention having the left handle shell removed, showing theactuators located to cause the upper jaw to be in the closed positionand the cutting element in a proximal position.

FIG. 14 is a top view of the handle assembly of FIG. 13, with the lefthandle shell assembled.

FIG. 15 is a longitudinal, sectional view of the distal portion of thetube assembly of the instrument of FIG. 13.

FIG. 16 is a side view of the handle assembly of the instrument of thepresent invention having the left handle shell removed, showing theacutators located such that the upper jaw is the closed position and thecutting element in a distal position.

FIG. 17 is a top view of the handle assembly of FIG. 16, with the lefthandle shell assembled.

FIG. 18 is a longitudinal, sectional view of the distal portion of thetube assembly of the instrument of FIG. 16.

FIG. 19 is an isometric view illustrating the instrument of the presentinvention being used in combination with an endoscopic surgicalretractor for surgically harvesting a vessel from a patient.

BEST MODE FOR CARRYING OUT THE INVENTION

The electrosurgical clamping, coagulating, and cutting instrument of thepresent invention is illustrated in FIG. 1 shown with a schematicrepresentation of an electrosurgical energy generator 6. Instrument 8 isseen to have a handle assembly 100 and a tube assembly 10 having adistal end section and a proximal end. Handle assembly 100 is seen to bemounted to the proximal end of tube 10. Handle assembly 100 furthercomprises a first actuator 104, a second actuator 102, and a power cord106 for electrical connection to electrosurgical energy generator 6. Anoperator actuates first actuator 104 for grasping and compressingtissue. The operator actuates second actuator 102 for cutting tissue.The operator presses a conventional foot switch (not shown) providedwith electrosurgical generator 6 for supplying bipolar electrosurgicalenergy to instrument 8.

Instrument 8 operates with numerous conventional, commerciallyavailable, electrosurgical energy generators. An example ofelectrosurgical energy generator 6 is a unitary mono-polar-bipolar RFgenerator, such as the Valleylab “FORCE 2” RF Generator manufactured byValleylab, a division of Tyco Healthcare Group LP, 5920 Longbow Drive,Boulder, Colo., 80301-3299, U.S.A.

Conventional power cord 106 may be long (for example, over two meters)and connect directly to electrosurgical energy generator 6 viastandardized, bipolar connectors, which are well-known in the art. Powercord 106 may also be short (less than one third of a meter, for example)and have a standardized, conventional bipolar connection (alsowell-known in the art) to another, longer power cord, which is normallyreusable and available with electrosurgical energy generator 6. Anoperator uses a foot-activated switch of electrosurgical energygenerator 6 to supply energy through instrument 8 to the tissue beingtreated. The operator adjusts the maximum power setting onelectrosurgical energy generator 6 to be in sufficiently effectiverange; for example a preferable range of approximately 20-60 watts,although instrument 8 operates at other conventional power settingsalso. The operator may press the foot switch and supply energy toinstrument 8 for a few seconds to coagulate the tissue being treated.Only a portion (about 3 watts) of this energy is conducted through thetissue due to the high resistivity of tissue and the use of offsetelectrodes as described earlier and hereinafter. The operator may useinstrument 8 to hemostatically seal a small (2-4 mm diameter) bloodvessel, for example, in less than one second, but the operator maycontinue to depress the foot switch a few more seconds if desired sincethere is believed to be practically no additional, lateral spreading ofthermal energy.

Referring now to FIG. 2, an isometric view of the distal portion orsection of tube assembly 10 of FIG. 1 is illustrated. An elongated,closing tube 14 is shown retracted to an open position, holding upperjaw 42 in an open position relative to a stationary, opposing, lower jaw44. Upper jaw 42 and lower jaw 44 are preferably injection molded from abiocompatible plastic such as polycarbonate or polyethylene or otherconventional biocompatible polymeric materials. Closing tube 14 ispreferably made from a stainless steel tube, although other conventionalbiocompatible materials may be used. The operator moves closing tube 14in the proximal direction with respect to handle assembly 100 to openupper jaw 42 by moving first actuator 104 (see FIG. 1) in the proximaldirection. The operator moves closing tube 14 in the distal direction toclose upper jaw 42 by moving first actuator 104 in the distal direction.

Referring to FIGS. 2 and 3, closing tube 14 is shown to comprise adistal portion or section 18 and a proximal portion or section 16.Distal portion 18 of closing tube 14 is seen to have, preferably, anapproximately rectangular, cross-sectional shape with a left surface 20,a right surface 21 (hidden), an upper surface 22, and a lower surface 23(hidden), with surfaces 22 and 23 being curved as shown.

Tube 14 may have other geometric cross-sections such as circular,polygonal, oval, square and combinations thereof. Distal portion 18 ofclosing tube 14 further comprises distally extending upper arm 30 andlower arm 28 separated by a left slot 32 on left surface 20, and anidentically shaped right slot 33 (hidden) on the right surface 21(hidden). Proximal portion 16 of closing tube 14 slides freely inside ofan elongated, tubular sleeve 12. Closing tube 14 and sleeve 12 arepreferably constructed from round tubing in this embodiment, but mayalso be constructed from tubing having other geometric shapes such as,for example, rectangular, oval, polygonal, combinations thereof and thelike. Although sleeve 12 may be made of a non-metallic material such asextruded polyethylene tubing, it is preferably metallic in order tocontribute significantly to the bending stiffness of tube assembly 10.In this embodiment, tube assembly 10 is relatively long and thin (forexample, fits through a 5 mm trocar) to enable the operator to useinstrument 8 for endoscopic vessel harvesting as will be described.

Closing tube 14 is further seen to have a tab 26 formed into uppersurface 22, which engages and opens upper jaw 42, as will be describedfor FIG. 9.

Still referring to FIGS. 2 and 3, upper jaw 42 is seen to have aplurality of upper teeth 58, and lower jaw 44 is seen to have aplurality of lower teeth 56, thus defining a tissue grasping region 57.Upper jaw 42 also includes an upper channel 54, and lower jaw 44includes a lower channel 52, for the longitudinal movement of a cuttingelement 70 (see FIG. 4) partially contained inside of lower channel 52.A left fin 64 and a right fin 65 extend from lower jaw 44 to preventcutting element 70 from cutting tissue when upper jaw 42 is in the openposition. Upper jaw 42 further includes a blunt, upper tip 48 (alsocalled a distal tip), and lower jaw 44 has a blunt, lower tip 46 (alsocalled a distal tip). Upper tip 48 and lower tip 46 help the operator tofunnel tissue into tissue grasping region 57. When upper jaw 42 is inthe closed position, upper tip 48 and lower tip 46 form a V-shaped,dissecting tip 50 as shown in FIG. 3, which is useful for separatingtissue layers as will be described. Upper arm 30 of closing tube 14slides on a top surface 62 of upper jaw 42. Lower arm 28 of closing tube14 slides on a bottom surface 60 of lower jaw 44. When lower jaw 42 isin the closed position as shown in FIG. 3, top surface 62 and bottomsurface 60 are almost completely covered by closing tube 14. Tissueclamped between upper jaw 42 and lower jaw 44 extends laterally out ofleft slot 32 and right slot 33 (hidden) of closing tube 14, contacting aleft lower edge 34 and a right lower edge 35 (see FIG. 4). A left flange66 of upper jaw 42 separates tissue from a left upper edge 36 of upperarm 30. A right flange 67 (hidden) of upper jaw 42 separates tissue froma right upper edge 37 (hidden) of upper arm 30.

Now referring to FIG. 4, an exploded, isometric view of the distalportion of tube assembly 10 is shown. Upper jaw 42 is seen to have adistal portion 55 and a proximal portion 53 joined together at a hinge49. Hinge 49 is sometimes referred to as a “living hinge” since it is athin, flexible area of the injection molded, upper jaw 42. Upper jaw 42also includes a cam follower 47 located near hinge 49, and a lip 43located on top surface 62. Lower jaw 44 includes a distal portion 59 anda proximal portion 51 joined together at a cam 45. Cam follower 47 ofupper jaw 42 rides against cam 45 of lower jaw 44.

As seen in FIG. 4, cutting element 70 comprises a proximal portion 80(partially shown), a distal portion 78, joined together at an offset 84.Proximal portion 80 comprises a longitudinal element 76 and is attachedto second actuator 102 shown in FIG. 1. Distal portion 78 and proximalportion 80 may be constructed from one piece of metal, or may beseparate metallic elements joined together, for example, by a weld,mechanical connectors, rivets, pins, etc., and the like. Distal portion78 is seen to have on the distal end a first blade 72 for cutting in theproximal direction and an opposed second blade 74 for cutting in thedistal direction. The blades may be made as part of the distal portion78 or mounted thereto by conventional methods such as welding, rivets,mechanical fasteners, etc. Lower jaw 44 contains cutting element 70 inlower channel 52 so that edge 82 of cutting element 70 is approximatelyflush with lower teeth 56. Proximal portion 80 of cutting element 70 isslidably contained in a right channel 95 of a right retainer 91, and ina left channel 96 (hidden) of a left retainer 90. Left and rightretainers, 90 and 91, are also referred to together as a shaft having aproximal and a distal end. Closing tube 14 slides freely over leftretainer 90 and right retainer 91, which are mounted to handle assembly100 of FIG. 1. Right retainer 91 and left retainer 90 are made from anelectrically non-conductive material such as plastic, for example, inorder to electrically isolate cutting element 70 from closing tube 14.As a secondary electrical barrier, cutting element 70 may also be coatedas desired with an insulative material. An example of a suitable coatingfor cutting element 70 is a thin sufficiently effective (for example,about 0.005 mm), vacuum deposited polymer well known in the art asparylene-n (also referred to as parylene), which is based on a highpurity raw material called di-paraxylylene. Edge 82 of distal portion 78of cutting element 70 functions as an electrode surface and comes intocontact with tissue held between upper jaw 42 and lower jaw 44. Edge 82(also referred to as a second electrode surface) is not coated withparylene-n or any other insulating material, and is a conductivesurface.

Still referring to FIG. 4, right retainer 91 is seen to include a righthook 93 extending distally from the distal end thereof for attachment toa right hook 99 extending proximally from proximal section 51 of lowerjaw 44. Left retainer 90 includes a left hook 92 for engagement with aleft hook 98 extending proximally from the proximal section 51 lower jaw44. As a result, lower jaw 44 is stationary relative to cutting element70 and closing tube 14. The operator actuates second actuator 102 tomove cutting element 70 in either longitudinal direction, and actuatesfirst actuator 104 to move closing tube 104 in either longitudinaldirection. Upper jaw 42 moves a short distance during opening andclosing in the longitudinal directions due to operational engagementwith closing tube 14, as will be described.

Sleeve 12 fits concentrically over closing tube 14 and strengthens tubeassembly 10 to resist bending as described earlier, and may be slidablymounted or fixedly mounted. Sleeve 12 also separates closing tube 14from external structures rubbing against it that may impede itsmovement, such as tissue layers or a trocar seal if used with a trocar.

FIG. 5 is a cross-sectional view of the distal end of tube assembly 10of FIG. 3, taken along View Lines 5—5. Left lower edge 34 (also referredto as a first conducting surface) and right lower edge 35 (also referredto as a second conducting surface) of lower arm 28 of closing tube 14(also referred to as a first electrode) have a first polarity, forexample, shown as positive. Spaced midway between left and right loweredges, 34 and 35, is edge 82 of cutting element 70 contained in lowerchannel 52 of lower jaw 44. Edge 82 has a second, opposite polarity, forexample, shown as negative. Edge 82 is laterally offset and electricalisolated from left and right lower edges, 34 and 35. Therefore, edge 82cannot electrically short to left and right lower edges, 34 and 35, ifthere is no tissue clamped between upper jaw 42 and lower jaw 44.However, bipolar electrosurgical current flows between edge 82 and leftlower edge 34 through tissue clamped in a left compression zone 88 andbipolar electrosurgical current flows between edge 82 and right loweredge 35 through tissue clamped in a right compression zone 89. Tissue iscoagulated simultaneously in both left compression zone 88 and rightcompression zone 89. Once this tissue is coagulated, tissue resistivityis increased and electrical conductivity is decreased. As a result, eventhough the operator may continue to supply bipolar electrosurgicalenergy to instrument 8 (by depressing the foot pedal control for theelectrosurgical energy generator 6 of FIG. 1), it is believed thateffectively no additional coagulation of tissue takes place. Moresignificantly, there is no electrical pathway outside of the clampedjaws, 42 and 44. Therefore, there is effectively no lateral thermalspread and coagulation of tissue outside of the jaws, 42 and 44. Leftupper edge 36 of closing tube 14 is electrically insulated from clampedtissue by left flange 66 of upper jaw 42. Right upper edge 37 of upperarm 30 of closing tube 14 is electrically insulated from clamped tissueby right flange 67 of upper jaw 42. First and second blades, 72 and 74,of cutting element 70 (see FIG. 4) extend into upper channel 54, to cuttissue contained between compression zones 88 and 89. Upper channel 54also serves as a vent for vapor to escape from upper jaw 42 during theapplication of RF energy.

As seen in FIG. 5, closing tube 14 has a substantially rectangularcross-section formed by upper surface 22, lower surface 23, left surface20, and right surface 21. The upper and lower surfaces 22 and 23 areseen to have a slightly curved configuration in a preferred embodiment.The rectangular cross-sectional configuration is believed to haveseveral advantages over, for example, a circular cross-sectionalconfiguration: the rectangular cross-sectional configuration allowsupper arm 30 and lower arm 28 to be stiffer so that deflection of upperarm 30 and lower arm 28 is minimized when tissue is clamped betweenupper jaw 42 and lower jaw 44; the rectangular cross-sectionalconfiguration allows better visualization of tissue structures on eachside of closing tube 14; the rectangular cross-sectional configurationhas a smaller footprint on the clamped tissue and allows a higherpressure to be applied to tissue for a given closing force applied, thusaiding in the formation of a hemostatic weld of the tissue.

The closing tube 14 is multifunctional in that it moves upper jaw 42between the open and closed positions, and it also serves as anelectrical conductor, with left and right lower edges, 34 and 35, beingused as outer electrodes of the same polarity. Similarly, cuttingelement 70 is multifunctional in that it not only cuts tissue heldbetween upper jaw 42 and lower jaw 44, but edge 82 of cutting element 70serves as an electrode having opposite polarity of closing tube 14. Bymaking closing tube 14 and cutting element 70 electrically activecomponents, it is not necessary to provide separate, spaced apart,bipolar electrodes in lower jaw 44. Consequently, the overall width oflower jaw 44 is significantly smaller than would be if separateelectrodes of opposite polarity were mounted in lower jaw 44. Thisenables the aforementioned benefits of a smaller footprint on thetissue. In addition, the number of components and the overall cost tomanufacture the instrument is reduced by the multifunctionality ofclosing tube 14 and cutting element 70.

Because instrument 8 incorporates offset electrodes technology and thetissue reaches a high coagulation temperature only very briefly, tissuedoes not char or burn as may occur when using conventional bipolarinstruments. Nevertheless, a small amount of sticking of tissue toelectrode surfaces in instrument 8 may still occur. In instrument 8,closing tube 14 moves longitudinally (i.e., proximally or distally) foreach time upper jaw 42 is opened or closed, thus causing the activeelectrical surfaces, right lower edge 35 and left lower edge 34, to moverelative to the stationary tissue held between upper jaw 42 and lowerjaw 44. This allows any tissue that may be adhering to right and loweredges, 34 and 35, after the application of energy and the coagulation oftissue, to break free. Similarly, each time the operator actuatescutting element 70 in either the proximal or distal direction, theelectrically active surface, edge 82 of cutting element 70, breaks freefrom adhering tissue. All electrically active surfaces in instrument 8are wiped against the tissue clamped for each cycle of operation(clamp/coagulate/cut/open), thus helping to keep those surfaces cleanand electrically conductive. In addition, when the operator opens upperjaw 42, the ends of the treated tissue are more likely to fall freelyfrom the jaws than if using conventional bipolar devices, and it is notnecessary to excessively manipulate instrument 8 to remove the tissue.

FIG. 6 is an exploded, isometric view of handle assembly 100, whichpreferably has an “in-line” style (as opposed to pistol-grip, etc.) inthis embodiment, but is not restricted to this style. A right handleshell 108 includes a plurality of bosses 160 for assembly to a matchingnumber of gripper pins 161 on left handle shell 110. Right and lefthandle shells, 108 and 110, are preferably injection molded from arigid, conventional, biocompatible plastic such as polycarbonate and thelike. The shells 108 and 110 support the following components: firstactuator 104, second actuator 102, power cord 106, a divider 112, abi-directional spring 114, and a sequencing lever 116 (also referred toas a sequencing element or operational sequencing element).

As described for FIG. 1, first actuator 104 is slidably mounted inhandle assembly 100 and controls the longitudinal movement of closingtube 14 for opening and closing upper jaw 42 (FIG. 2). When the operatormoves first actuator 104 distally from an open position to a distalclosed position, upper jaw 42 closes. When the operator moves firstactuator 104 proximally from the closed position to the open position,upper jaw 42 opens. First actuator 104 does not have a return spring orany other means for providing a biasing force to either the extended oropen position in this preferred embodiment, although it is possible andwithin the scope of this invention to do so.

Second actuator 102 controls the longitudinal movement of cuttingelement 70. When the operator moves second actuator 102 in the proximaldirection from a central position to a proximal position, first blade 72(FIG. 4) of cutting element 70 moves proximally and cuts through tissueclamped between upper jaw 42 and lower jaw 44 within tissue graspingregion 57 (FIG. 2). When the operator releases second actuator 102, itmoves from the proximal position back to the central position due to thebiasing force provided by bi-directional spring 114 (preferably ahelical coil spring). As cutting element 70 moves distally from theproximal position to the central position, second blade 74 (FIG. 4) ofcutting element 70 cuts a second time through tissue clamped betweenupper jaw 42 and lower jaw 44. When the operator moves second actuator104 in the distal direction from the central position to a distalposition, cutting element 70 extends distally so that second blade 74(FIG. 4) is exposed to tissue adjacent to dissecting tip 50, allowingthe operator to separate tissue layers and cut through tissue distallyadjacent to dissecting tip 50 as the operator advances instrument 8 inthe distal direction. When the operator releases second actuator 102,cutting element 70 moves proximally and again returns to the centralposition due to the biasing force provided by bi-directional spring 114.A biasing force is provided for cutting element 70 in this embodiment sothat first and second cutting blades, 72 and 74, are safely containedbetween left and right fins, 64 and 65, of lower jaw 44 when theoperator is not actuating second actuator 102. In another embodiment ofthe present invention, bi-directional spring 114 may be eliminated sothat movement of the cutting element 14 is possible only when theoperator moves second actuator 104.

Still referring to FIG. 6, second actuator 102 is seen to have a frame103 that supports bi-directional spring 114, which is a helical coilwire compression spring in a preferred embodiment. If desired, othertypes of conventional springs may be used such as leaf springs, etc. Arail 132 on frame 103 of second actuator 102 rides inside of a righttrack 130 of right handle shell 108, so that bi-directional spring 114is trapped between a first stop 126 and a second stop 128 of righthandle shell 108. Second actuator 102 includes a mount member 136 havinga projection 137 for insertion into and engagement with a notch 154 oncutting element 70, so that longitudinal translation of second actuator104 causes an equal longitudinal translation of cutting element 70 inthe same direction. First actuator 104 is seen to have a bar slider 163,which rides on a left track 131 (hidden) on the inside of left handleshell 110. First actuator 104 also has a closing block 164 that containsa pair of slots 165 (hidden) for receiving a pair of tabs 172 extendingradially on the proximal end of closing tube 14, so that longitudinaltranslation of first actuator 102 causes an equal longitudinaltranslation of closing tube 14 in the same direction. Closing block 164is supported and guided also by a right shelf 162 in right handle shell108 and a left shelf 155 (hidden) in left handle shell 110. Firstactuator 104 and second actuator 102 are separated by divider 112 havinga top fin 142 to help prevent the operator from actuating first andsecond actuators, 104 and 102, at the same time. Divider 112 alsoprovides a tactile, positional reference for the operator to know therelative positions of first and second actuators, 104 and 102, withoutlooking at them. A first tab 138 and a second tab 140 extending offopposite ends of divider 112 mount divider 112 to a first support 146and a second support 148, respectively, of right handle shell 108. Ayoke 144 on divider 112 mounts onto a right retaining fin 150 of righthandle shell 108 and a similar, left retaining fin 151 (hidden) on theinside of left handle shell 110. First actuator 104, second actuator102, and divider 112 are preferably injection molded from a rigid,biocompatible plastic such as polycarbonate, although many otherconventional materials may also be used.

Still referring to FIG. 6, an optional, although preferred, sequencinglever 116 (also referred to as a sequencing element) ensures the propersequence of operation of first and second actuators, 104 and 102. Morespecifically, sequencing lever 116 locks out second actuator 102 frommoving to the proximal position (moving cutting element 70 to theproximal position) unless first actuator 104 is at the closed position(for when upper jaw 42 is closed and tissue is clamped). When tissue hasbeen clamped for a period of time and electrosurgically coagulated, thetissue becomes less elastic and clamping force relaxes. To severe thecoagulated tissue hemostatically, however, it is important that thecoagulated tissue continue to be held firmly between upper and lowerjaws, 104 and 102, so that cutting element 70 cuts through the middle ofthe coagulated tissue. This leaves an equal margin of coagulated tissueon each of the severed ends of the tissue so that the transection ishemostatic. Sequencing lever 116 also prevents first and second blades,72 and 74, from being exposed to tissue in tissue grasping region 57(FIG. 2) between upper and lower jaws, 42 and 44, while the operatorpositions instrument 8 prior to clamping, thus preventing inadvertentcutting of the tissue. Sequencing lever 116 also prevents first actuator104 from moving from the closed position to the open position (to openupper jaw 42) unless second actuator 102 is safely in the distal orcentral positions and first and second blades, 72 and 74, are not intissue clamping region 57. Sequencing lever 116 is preferably made ofstainless steel, although it may be injection molded from a rigid, highstrength plastic or other conventional materials. Sequencing lever 116has a hole 168 that mounts pivotably onto post 166 of right handle shell108, and a slot 170 for operational engagement with a first pin 134extending off of frame 103 of second actuator 102.

FIG. 6 depicts a portion of power cord 106 having a strain reliever 174that inserts between a pair of bosses 160 in right handle shell 108.Power cord 106 also includes an electrically insulated, first conductor118 terminating with a first connector 122 for electrical attachment tocutting element 70, and an electrically insulated, second conductor 120terminating with a second connector 124 for electrical attachment toclosing tube 14. First and second connectors, 122 and 124, are shown inthis embodiment to be configured for quick assembly, although variousother types of connectors well known in the art or soldering and otherconventional mounting techniques may be used in this application. Theconductors are made from conventional conducting materials includingcopper wire, aluminum wire and the like and equivalents thereof.

Still referring to FIG. 6, it can be seen that handle assembly 100retains tube assembly 10 as follows: left and right retainers, 90 and91, have a pair of opposing recesses 152 for staking to left and rightretaining fins, 151 (hidden) and 150. Sleeve 12 has a pair of opposingslits 156 (one is hidden) for retention in a right cradle 158 of righthandle shell 108 and a left cradle 157 (hidden) of left handle shell110. A holder 159 supports sleeve 12.

Now referring to FIG. 7, a side view of handle assembly 100 without leftshell 110 reveals the orientation of sequencing lever 116 for when firstactuator 104, attached to closing tube 14, is in the open position andsecond actuator 102 (substantially hidden by fin 142) is in the centralposition. First pin 134, which extends from frame 103 of second actuator104 rests in slot 170 of sequencing lever 116. Closing block 164 offirst actuator 104 prevents rotation of sequencing lever 116 about post166, thereby causing slot 170 to be inclined relative to thelongitudinal axis of handle assembly 100, and preventing movement in theproximal (right) direction of second actuator 102. As FIG. 7 shows, alever end 117 cannot move in the clockwise direction until a closingblock corner 169 is distal to it, thus preventing movement of secondactuator 104 in the distal direction. Bi-directional spring 114 isslightly compressed within frame 103, but does not exert a biasing forceon second actuator 102 in either longitudinal direction.

FIG. 8 is a top view of handle assembly 100 showing the positions offirst actuator 104 and second actuator 102 (separated by fin 142)corresponding with FIG. 7.

FIG. 9 is a cross-sectional view of the distal portion of tube assembly10, and corresponds with FIGS. 7 and 8. Closing tube 14 is in the openposition so that tab 26 engages a lip 43 of upper jaw 42, causing afollower 47 of upper jaw 42 to ride up on a cam 45 of lower jaw 44, thuscausing upper jaw 42 to flex at a hinge 49 of upper jaw 42 to the openposition. Cutting element 70 is in the central position with first blade72 and second blade 74 protected by left fin 64 (removed in this view)and right fin 65. When upper jaw 42 closes against lower jaw 44, cam 45and left and right fins, 64 and 65, contain tissue to be clamped intissue grasping region 57, ensuring that tissue to be treated does notsqueeze out the distal end of the upper and lower jaws, 42 and 44, asmay occur in other surgical grasping instruments. The wiping action offollower 47 against cam 45 also ensures that tissue is not pinched inbetween upper and lower jaws, 42 and 44, such as may occur in othersurgical grasping instruments.

FIG. 10 is a side view of handle assembly 100 with left shell 110removed to reveal the position of sequencing lever 116 for when firstactuator 104 is in the closed position and second actuator 102(substantially hidden by fin 142) is in the central position. Closingblock corner 169 of closing block 164 is distal to lever end 117, thusallowing rotation of sequencing lever 116 about post 166, and proximaltranslation of second actuator 102. As first pin 134 extending off frame103 translates proximally, slot 170 moves from the steeply inclinedorientation shown in FIG. 10 to a less inclined position as shown inFIG. 13. Bi-directional spring 114 is in the same configuration for FIG.10 as for FIG. 7, and is not providing a biasing force in eitherlongitudinal direction to second actuator 104.

FIG. 11 corresponds with FIG. 10 and shows a top view of handle assembly100 for when first actuator 104 is in the closed position and secondactuator 102 is in the central position, with fin 142 between firstactuator 104 and second actuator 102.

FIG. 12 is a sectional view of the distal portion of tube assembly 10corresponding with FIGS. 10 and 11. Upper jaw 42 is in the closedposition and tab 26 of closing tube 14 is separated from lip 43 of upperjaw 42. Follower 47 of upper jaw 42 abuts cam 45 of lower jaw 44 so thatupper jaw 42 fits tightly against lower jaw 44 with very minimal airgaps there between. This ensures that tissue may be securely clampedduring coagulation and cutting, and provides an additional electricalbarrier between cutting element 70 and closing tube 14. First blade 72and second blade 74 are in the central position and safely separatedfrom tissue that may be clamped between upper jaw 42 and lower jaw 44.Dissecting tip 50 may be used in this configuration as a blunt dissectorand tissue layer separator without cutting.

FIG. 13 is a side view of handle assembly 100 with left shell 110removed to reveal the position of sequencing lever 116 for when firstactuator 104 is in the closed position and second actuator 102 is in theproximal position. Fin 142 provides a tactile reference for the operatorto feel the change of position for first and second actuators, 104 and102. Closing block corner 169 of closing block 164 is distal to leverend 117 so that sequencing lever 116 rotates about post 166 when firstpin 134 translates proximally within slot 170. Bi-directional spring 114is compressed between frame 103 of second actuator 102 and second stop128 of handle shell 108, thus providing a biasing force in the distaldirection (and urging second actuator 104 to move from the proximalposition to the central position.)

FIG. 14 is a top view of handle assembly 100 corresponding with FIG. 13for when first actuator 104 is in the closed position and secondactuator 102 is in the proximal position. Fin 142 separates first andsecond actuators, 104 and 102.

FIG. 15 is a sectional view of the distal portion of tube assembly 10corresponding to FIGS. 13 and 14. Upperjaw 42 is in the closed positionwith closing tube 14 substantially covering upper jaw 42 and lower jaw44. Cutting element 70 is shown in the proximal position with firstblade 72 having made a first cut through tissue that may have beenclamped between upper and lower jaws, 42 and 44. Second blade 74 ispositioned to make a second pass through the tissue upon release ofsecond actuator 104 (FIG. 13).

FIG. 16 is a side view of handle assembly 100 with left handle shell 110removed and shows the position of sequencing lever 116 for when firstactuator 104 is in the closed position and second actuator 102(substantially hidden by fin 142) is in the distal position. Closingblock corner 169 of closing block 164 is again distal to lever end 117,although this is not necessary for pin 134 to move in the distaldirection inside of slot 170 of sequencing lever 116. Bi-directionalspring 114 is compressed between first stop 126 of right handle shell108 and frame 103 of second actuator 104, thus providing a biasing forceto second actuator 104 in the proximal direction.

FIG. 17 is a top view of handle assembly 100 corresponding with FIG. 16,and shows first actuator 104 in the closed position. Fin 142 separatesfirst actuator 104 from second actuator 102, which is in the distalposition. The operator must hold second actuator 104 in the distalposition due to the biasing force, which bi-directional spring 114provides.

FIG. 18 is a sectional view of the distal portion of tube assembly 10,corresponding with FIGS. 16 and 17. Closing tube 14 surrounds upper jaw42 and lower jaw 44 in the closed position. Cutting element 70 is in thedistal position so that second blade 74 extends partially into theV-shape opening of dissecting tip 50 and is able to sever tissue thatwould be distally adjacent to dissecting tip 50. Second blade 72 isstill protected within upper jaw 42 and lower jaw 44.

FIG. 19 is a isometric view of instrument 8 being used for a surgicalprocedure in combination with a surgical retractor 200 forendoscopically harvesting a vessel 224 from a surgical patient 220 foruse in a coronary artery bypass graft (CABG) surgical procedure.Retractor 200 and its method of use are disclosed in U.S. Pat. Nos.5,928,138 and 5,928,135 and are hereby incorporated herein forreference. Retractor 200 comprises a grip 204 attached to the proximalend of an endoscopic shaft 208, which may be inserted into an incision226. A spoon element 206 is attached to the distal end of endoscopicshaft 208. The operator manipulates retractor 200 to advance a spoonshaped, working head 206 along vessel 224, separating tissue from vessel224 and providing a working space for accessing and visualizing vessel224 and a plurality of side branches 222. A port 202 provides access foran endoscope (not shown) for visualization within working head 206. Anozzle 210 may connect to a low pressure, carbon dioxide gas source forclearing away vapor and smoke from within the working space insideworking head 206. Tube assembly 10 of instrument 8 inserts throughincision 226 underneath shaft 208 of retractor 200. Tube assembly 10could also be inserted through a port in an endoscope or retractor orendoscopic vein harvesting instrument. The operator manipulatesinstrument 8 within the working space inside working head 206 todissect, clamp, coagulate, and cut tissue as described for FIGS. 7-18.In particular, side branches 222 are coagulated and cut without damagingharvested vessel 224. The length of tube assembly 10 may vary, butpreferably is long enough for handle assembly 100 to be proximal to theendoscope inserts into port 202 while tube assembly 10 is inserted farenough into patient 220 to access the working space within working head206. Instrument 8 may be used with other conventional retractors andvein harvesting instruments.

Instrument 8 is especially suited for vessel harvesting as described forFIG. 19, but is not limited to only this surgical procedure. Instrument8 may also be used to dissect, clamp, coagulate, and cut tissues duringnumerous other types of endoscopic and open surgical procedures.Instrument 8, as described in the present embodiment, is intended forsingle patient use. Instrument 8 may be constructed, however, frommaterials and using techniques, allowing resterilization and reuse onmore than one surgical patient.

Although this invention has been shown and described with respect todetailed embodiments thereof it will be understood by those skilled inthe art that various changes in form and detail thereof may be madewithout departing from the spirit and scope of the claimed invention.

What is claimed is:
 1. A surgical instrument for cutting tissuecomprising: a handle having a distal end, a proximal end, a top, and abottom; a shaft having a proximal end, a distal end, and a longitudinalaxis, wherein the proximal end of the shaft is mounted to the proximalend of the handle; a first jaw and an opposed second jaw mounted to thedistal end of the shaft, the first and second jaws movable relative toeach other from an open position for positioning tissue therebetween ina tissue grasping region, to a closed position for approximating tissue,each jaw having a proximal end and a distal end, the first jaw having afirst channel and the second jaw having a second channel, wherein thefirst and second channels form a cutting tunnel when the first andsecond jaws are in the closed position; an elongated member slidablymounted to the shaft, said elongated member having a proximal end and adistal end; a cutting element movable within the cutting tunnel to cuttissue positioned between the first and second jaws in the tissuegrasping region, the cutting element mounted to the distal end of theelongated member, the cutting element having a first blade and a secondblade, the cutting element movable in the cutting tunnel from a centralposition to a proximal position proximal to the tissue grasping regionand a distal position distal to the tissue grasping region, wherein thefirst blade cuts tissue positioned between the first and second jawswhen the cutting element moves from the central position to a proximalposition, and the second blade cuts tissue positioned between the firstand second jaws when the cutting element moves from the proximalposition to the central position; an actuating member mounted to thehandle, wherein the proximal end of the elongated member is mounted tothe actuating member; and a dissecting tip is formed by the distal endsof the first and second jaws, the dissecting tip having a distal end andcovering the cutting element when the cutting element is in the centralposition so that adjacent tissue is shielded from the first and secondcutting blades, and wherein the cutting tunnel extends through thedistal end of the dissecting tip and is in communication with an openingin the distal end of the dissecting tip, such that when the cuttingelement is moved from the central position to the distal position, atleast a section of the second cutting blade extends out through thedissecting tip and out of the cutting tunnel such that the secondcutting blade may engage tissue.
 2. The instrument of claim 1, whereinthe dissecting tip comprises a V-shape.
 3. The surgical instrument ofclaim 1, wherein the dissecting tip additionally comprises a pair offins projecting laterally outward from the distal end of the first jawsuch that the fins provide a shield to prevent tissue from contactingthe cutting element when the jaws are in the open position.
 4. Theinstrument of claim 1, wherein the shaft comprises an inner lumen andthe elongated member is slidably mounted in the lumen.
 5. The instrumentof claim 1, wherein the handle comprises a hollow cavity, and theproximal end of the elongated member extends into the handle.
 6. Theinstrument of claim 5, wherein the actuating member comprises a memberslidably mounted to the top of the handle and having a bottom and a top,the bottom extending into the cavity, wherein the proximal end of theelongated member is mounted thereto.
 7. The instrument of claim 1,additionally comprising a member slidably mounted to the shaft formoving the first and second jaws between an open position and a closedposition.
 8. A method of surgically cutting tissue, the methodcomprising the steps of: a. providing a surgical instrument, theinstrument comprising: a handle having a distal end, a proximal end, atop, and a bottom; a shaft having a proximal end, a distal end, and alongitudinal axis, wherein the proximal end of the shaft is mounted tothe proximal end of the handle; a first jaw and an opposed second jawmounted to the distal end of the shaft, the first and second jawsmovable relative to each other from an open position for positioningtissue therebetween in a tissue grasping region, to a closed positionfor approximating tissue, each jaw having a proximal end and a distalend, the first jaw having a first channel and the second jaw having asecond channel, wherein the first and second channels form a cuttingtunnel when the first and second jaws are in the closed position; anelongated member slidably mounted to the shaft, said elongated memberhaving a proximal end and a distal end; a cutting element movable withinthe cutting tunnel to cut tissue positioned between the first and secondjaws, the cutting element mounted to the distal end of the elongatedmember, the cutting element having a first blade and a second blade, thecutting element movable in the cutting tunnel from a central position toa proximal position proximal to the tissue grasping region and a distalposition distal to the tissue grasping region, wherein the first bladecuts tissue positioned between the first and second jaws when thecutting element moves from the central position to a proximal position,and the second blade cuts tissue positioned between the first and secondjaws when the cutting element moves from the proximal position to thecentral position; an actuating member mounted to the handle, wherein theproximal end of the elongated member is mounted to the actuating member;and, a dissecting tip formed by the distal ends of the first and secondjaws, the dissecting tip having a distal end and covering the cuttingelement when the cutting element is in the central position so thatadjacent tissue is shielded from the first and second cutting blades,and wherein the cutting tunnel extends through the distal end of thedissecting tip and is in communication with an opening in the distal endof the dissecting tip, such that when the cutting element is moved fromthe central position to the distal position, at least a section of thesecond cutting blade extends out of the cutting tunnel and out throughthe opening in the dissecting tip such that the second cutting blade mayengage tissue; b. moving the jaws to the closed position; c. moving thecutting element from the central position to the distal position suchthat the second blade extends at least partially from the distal end ofthe dissecting tip; and, d. dissecting tissue with the second blade.